Lighting device

ABSTRACT

A lighting device includes a light guide that propagates incoming light, and a lighting panel including a lighting region. A front side of the lighting panel excluding the lighting region is configured to prevent transmission of light, the light guide is covered by the lighting panel, the lighting device is configured such that the light emitted from the light guide passes through the lighting region of the lighting panel for illumination, and surfaces of the lighting panel surrounding the light guide are white in color.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application filed under 35U.S.C. 111(a) claiming benefit under 35 U.S.C. 120 and 365(c) of PCTInternational Application No. PCT/JP2018/038272, filed on Oct. 15, 2018,which is based on and claims priority to Japanese Patent Application No.2017-230112 filed on Nov. 30, 2017, the entire contents of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

An aspect of this disclosure relates to a lighting device.

2. Description of the Related Art

Inside of an automobile, a lighting device including an annular lightguide and a light-emitting element such as a light-emitting diode (LED)is often provided to improve the visibility of an operation part such asa push button or a jog dial. A lighting region of such a lighting devicepreferably emits light with even and uniform luminance. For thispurpose, a related-art lighting device has a configuration whereprotrusions are provided on a light-emitting surface of a light guide(see, for example, Japanese Unexamined Patent Application PublicationNo. 2015-111520, Japanese Unexamined Patent Application Publication No.2015-111519, and Japanese Unexamined Patent Application Publication No.2003-215584).

Also, there is an automobile including an operation switch for operatinga power seat in the automobile, and a lighting device is often providedaround such an operation switch. Such a lighting device, for example,has a shape imitating the side shape of the power sheet and emits lightto facilitate operations of the operation switch at night.

The side shape of a power seat is not formed of simple straight lines ora circle, but is a complex shape formed by combining straight lines andmultiple curves with different curvatures. Accordingly, the luminance ofthe lighting device may vary between a portion having a larger curvature(a portion having a smaller radius of curvature), and a portion having asmaller curvature (a portion having a larger radius of curvature) and astraight portion. If the luminance of a lighting device becomes uneven,the quality of the lighting device may be reduced, and the luxuriousnessmay be reduced. Particularly, such uneven luminance is not desirable fora luxury car.

SUMMARY OF THE INVENTION

In an aspect of this disclosure, there is provided a lighting deviceincluding a light guide that propagates incoming light, and a lightingpanel including a lighting region. A front side of the lighting panelexcluding the lighting region is configured to prevent transmission oflight, the light guide is covered by the lighting panel, the lightingdevice is configured such that the light emitted from the light guidepasses through the lighting region of the lighting panel forillumination, and surfaces of the lighting panel surrounding the lightguide are white in color.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a power seat switch including a lightingdevice according to an embodiment;

FIG. 2 is a front view of the power seat switch including the lightingdevice according to the embodiment;

FIG. 3 is a perspective view of the power seat switch from which knobsand a lighting panel are removed;

FIG. 4 is a front view of the power seat switch from which the knobs andthe lighting panel are removed;

FIG. 5 is a perspective view of a light guide of the lighting deviceaccording to the embodiment;

FIG. 6 is a rear view of the light guide of the lighting deviceaccording to the embodiment;

FIG. 7 is a front view of the light guide of the lighting deviceaccording to the embodiment;

FIG. 8 is a drawing illustrating light-emitting elements of the lightingdevice according to the embodiment;

FIG. 9 is a drawing illustrating protrusions;

FIG. 10 is another drawing illustrating the protrusions;

FIG. 11 is a perspective view of a lighting panel of the lighting deviceaccording to the embodiment;

FIG. 12 is a front view of the lighting panel of the lighting deviceaccording to the embodiment;

FIG. 13 is a rear view of the lighting panel of the lighting deviceaccording to the embodiment;

FIG. 14 is a perspective view of the light guide placed in the lightingpanel;

FIG. 15 is a rear view of the light guide placed in the lighting panel;

FIG. 16 is a drawing illustrating the lighting device according to theembodiment; and

FIG. 17 is another drawing illustrating the lighting device according tothe embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

For the reasons described above, there is a demand for a lighting deviceincluding a lighting region that has a complex shape and can still emitlight with uniform luminance.

An embodiment of the present invention is described below with referenceto the accompanying drawings. The same reference number is assigned tothe same component throughout the drawings, and repeated descriptions ofthe same component may be omitted.

(Power Seat Switch)

First, a power seat switch including a lighting device according to thepresent embodiment is described. FIG. 1 is a perspective view and FIG. 2is a front view of the power seat switch. The power seat switch isdisposed, for example, on the inner side of a door of an automobile.Specifically, a lighting panel 20 is attached to the inner side of thedoor, and knobs 31 and 32 for operating the power seat switch areprovided on the lighting panel 20. In the descriptions of the presentembodiment, it is assumed that a housing 10 corresponds to the innerside of the door. For example, a switch body for controlling themovement of the power seat and a mechanism for operating the switch bodyare provided inside of the housing 10.

The lighting panel 20 is shaped like a box and includes a lightingregion 21 through which light leaks. Except for the lighting region 21,the outer side of the entire lighting panel 20 has a black color. Thelighting region 21 has an annular shape that imitates the side shape ofthe power seat. The knobs 31 and 32 are directly touched and manipulatedby a person (user) to operate the power seat switch and are attached tothe outer side of the lighting panel 20. The knob 31 is an operationpart for operating a portion of the power seat corresponding to theupper body, and the knob 32 is an operation part for operating a portionof the power seat corresponding to the lower body. The knobs 31 and 32are disposed in positions in a region inside of (or surrounded by) thelighting region 21 such that the user can intuitively recognize thecorresponding portions of the power seat.

As illustrated in FIG. 3 and FIG. 4, a light guide 40 corresponding tothe shape of the lighting region 21 of the lighting panel 20 is providedinside of the lighting panel 20. FIG. 3 is a perspective view and FIG. 4is a front view of the power seat switch from which the lighting panel20 and the knobs 31 and 32 are removed. As described later, the powerseat switch includes light-emitting elements such as LEDs, and lightemitted from the light-emitting elements enter the light guide 40.Multiple protrusions are provided on the surface of the light guide 40,and light is scattered by and output from the protrusions. The lightfrom the inside of the lighting panel 20 leaks to the outside throughthe lighting region 21 of the lighting panel 20. As a result, thelighting region 21 of the lighting panel 20 having a shape imitating theside shape of the power seat emits light, and the user can recognize thepositions of the knobs 31 and 32 for operating the power seat switcheven at night.

(Light Guide)

Next, the light guide 40 of the lighting device of the presentembodiment is described with reference to FIGS. 5 through 7. FIG. 5 is arear perspective view, FIG. 6 is a rear view, and FIG. 7 is a front viewof the light guide 40. The light guide 40 is formed of, for example, alight-transmitting transparent resin material such as transparentpolycarbonate. The light guide 40 is provided to cause the lightingregion 21 of the lighting panel 20 to emit light and therefore has ashape corresponding to the shape of the lighting region 21, i.e., ashape imitating the side shape of the power seat. The light guideincludes linear sections 40 a, 40 b, 40 c, and 40 d, smaller-curvaturecurved sections 40 e and 40 f having smaller curvatures, andlarger-curvature curved sections 40 g and 40 h having larger curvatures.

Multiple protrusions 42 are provided on a radiating surface 41 on thefront side of the light guide 40, i.e., on the surface facing the innerside of the lighting panel 20, to radiate light. The light guide 40 alsoincludes supports 43 a and 43 b near the larger-curvature curvedsections 40 g and 40 h disposed at the corresponding ends of the lightguide 40. Connecting sections 44 a and 44 b are provided inside of thesupports 43 a and 43 b.

Specifically, the connecting section 44 a having a curvature smallerthan the curvature of the larger-curvature curved section 40 g of thelight guide 40 is provided inside of the larger-curvature curved section40 g. The larger-curvature curved section 40 g and the connectingsection 44 a are connected at connecting parts 45 a and 45 b of thelight guide 40, and the support 43 a is disposed between thelarger-curvature curved section 40 g and the connecting section 44 a.Similarly, the connecting section 44 b having a curvature smaller thanthe curvature of the larger-curvature curved section 40 h of the lightguide 40 is provided inside of the larger-curvature curved section 40 h.The larger-curvature curved section 40 h and the connecting section 44 bare connected at connecting parts 45 c and 45 d of the light guide 40,and the support 43 b is disposed between the larger-curvature curvedsection 40 h and the connecting section 44 b.

As illustrated in FIG. 8, the lighting device of the present embodimentincludes light-emitting elements 51 and 52 such as LEDs. A light guide61 is provided between the light-emitting element 51 and the light guide40, and a light guide 62 is provided between the light-emitting element52 and the light guide 40. The light-emitting elements 51 and 52 arewhite LEDs and emit white light.

The light emitted from the light-emitting element 51 enters an end 61 aof the light guide 61, propagates through the light guide 61, isreflected by a reflecting surface 61 b at the other end of the lightguide 61, enters entry parts 40 m and 40 n of the light guide 40, andpropagates through the light guide 40. Similarly, the light emitted fromthe light-emitting element 52 enters one end of the light guide 62,propagates through the light guide 62, is reflected by a reflectingsurface at the other end of the light guide 62, enters the light guide40, and propagates through the light guide 40. Thus, the light emittedfrom the two light-emitting elements 51 and 52 enters the light guide 40and propagates through the light guide 40.

The refractive index of polycarbonate forming the light guide 40 isabout 1.59, and the refractive index of air is about 1. Accordingly,when light enters the light guide 40, the light is totally reflected atthe interface, e.g., the side surface of the light guide 40, between thelight guide 40 and the air, and propagates through the light guide 40.In the light guide 40, multiple protrusions 42 are provided on theradiating surface 41 for emitting light. Light is scattered by theprotrusions 42 and emitted from the radiating surface 41 to the outsideof the light guide 40.

In the present embodiment, as illustrated in FIG. 7, the intervalbetween the protrusions 42 is relatively wide near the light-emittingelements 51 and 52 and becomes narrower as the distances from thelight-emitting elements 51 and 52 increase so that the light isuniformly emitted from the radiating surface 41 of the light guide 40.Also, in the linear sections 40 a, 40 b, 40 c, and 40 d and thesmaller-curvature curved sections 40 e and 40 f, the interval betweenthe protrusions 42 is relatively wide; and in the larger-curvaturecurved sections 40 g and 40 h, the interval between the protrusions 42is relatively narrow.

As illustrated in FIGS. 9 and 10, the side shape of each protrusion 42may be a semi-cylindrical convex shape instead of a rectangular shape.FIG. 9 is a side view and FIG. 10 is a perspective view of a portion ofthe light guide 40 where the protrusions 42 are formed. The protrusion42 has a semi-cylindrical convex shape and includes a top part 42 ahaving a curved surface and a flat part that extends continuously froman end of the top part 42 a and has a flat surface. As illustrated inFIG. 10, light entering the protrusion 42 also exits from the curvedsurface of the top part 42 a of the protrusion 42, and the light exitingfrom the curved surface of the top part 42 a scatters at various angles.As a result, the proportion of light emitted from the radiating surface41 increases. For example, this makes it possible to prevent a problemwhere a large amount of light exits from a surface perpendicular to theradiating surface 41 of the light guide 40 in a direction along theradiating surface 41 and the light intensity becomes uneven. Also,because the top part 42 a of the protrusion 42 has a curved surface andis not sharp, the protrusion 42 is less likely to be damaged. Theprotrusion 42 may have a smooth surface. However, forming the protrusion42 to have a rough surface makes it possible to more effectively scatterthe light. The protrusion 42 may be formed to have a rough surface bynot performing a finishing process when producing a mold used to formthe light guide 40. The light guide 40 may be formed of, for example,polycarbonate or an acrylic resin having high light transmittance.

Here, as illustrated in FIGS. 5 through 7, the light guide 40 includesthe larger-curvature curved sections 40 g and 40 h that have a smallradius of curvature. In the larger-curvature curved sections 40 g and 40h, because the radius of curvature is small, the proportion of lightentering the side surface of the light guide 40 at an angle smaller thanthe critical angle becomes high. The light entering the side surface ofthe light guide 40 at an angle smaller than the critical angle leaks outof the light guide 40. For example, in the case of polycarbonate whoserefractive index is about 1.59, light entering the side surface of thelight guide 40 at an incident angle of less than or equal to 39 degreesleaks out of the light guide 40. The light leaked from the side surfaceof the light guide 40 is not directed to the lighting region 21. Whenthe leakage of light increases in the larger-curvature curved sections40 g and 40 h of the light guide 40, the amount of light propagatingthrough the larger-curvature curved sections 40 g and 40 h and thefollowing sections decreases. Therefore, dark portions may be generatedin the lighting region 21 of the lighting panel 20, and the luminance inthe lighting region 21 becomes uneven.

(Lighting Panel)

Next, the lighting panel 20 of the lighting device of the presentembodiment is described with reference to FIGS. 11 through 13. FIG. 11is a rear perspective view, FIG. 12 is a front view, and FIG. 13 is arear view of the lighting panel 20.

The lighting region 21 is provided on a front side 22 of the lightingpanel 20, and an outer wall 23 protruding backward from the periphery ofthe front side 22 of the lighting panel 20 and an inner wall 24 disposedinside of the outer wall 23 and protruding backward are provided on theback side of the lighting panel 20. In the lighting panel 20, thelighting region 21 is disposed between the outer wall 23 and the innerwall 24, and a groove 25 is formed by the outer wall 23 and the innerwall 24 on the back side of the lighting panel 20. Through holes 26 a,26 b, 26 c, and 26 d for connecting the knobs 31 and 32 to, for example,internal switches are formed in the front side 22 of the lighting panel20.

The lighting panel 20 is formed of, for example, a white resin such aswhite polycarbonate. The entire outer surfaces of the outer wall 23 andthe front side 22 of the lighting panel 20 excluding the lighting region21 are painted in black to prevent transmission of light. For example,two-component acrylic urethane paint is used for the black painting.With this configuration, a part of light is transmitted from the insideof the lighting panel 20 to the outside only in the lighting region 21of the lighting panel 20 and as a result, the lighting region 21 emitslight. In the present embodiment, the lighting panel is configured suchthat the transmittance of light through the lighting region 21 becomesabout 35%.

In the lighting device of the present embodiment, as illustrated inFIGS. 14 through 16, the light guide 40 is placed in the groove 25between the outer wall 23 and the inner wall 24 of the lighting panel20. Accordingly, when the light guide 40 is in the groove 25, an innersurface 23 a of the outer wall 23 faces the light guide 40, and an outersurface 24 a of the inner wall 24 faces the light guide 40. FIG. 14 is aperspective view, FIG. 15 is a rear view, and FIG. 16 is an enlargedcross-sectional view of the light guide 40 placed in the groove 25 ofthe lighting panel 20.

On the back side of the lighting panel 20 of the lighting device of thepresent embodiment, the inner surface 23 a of the outer wall 23 and theouter surface 24 a of the inner wall 24 of the lighting panel 20 formingthe groove 25 are not painted in black and are white in color. That is,in the groove 25, the surfaces surrounding the light guide 40 are whitein color. Therefore, light is reflected by the inner surface 23 a of theouter wall 23 and the outer surface 24 a of the inner wall 24 of thelighting panel 20.

As described above, in the larger-curvature curved sections 40 g and 40h of the light guide 40, light tends to leak to the outside of the lightguide 40. However, in the present embodiment, the leaked light isreflected by the white inner surface 23 a of the outer wall 23 and thewhite outer surface 24 a of the inner wall 24 and returns to the insideof the light guide 40 or enters the lighting region 21 of the lightingpanel 20. This configuration makes it possible to prevent the lightingregion 21 from becoming dark.

Specifically, as illustrated in FIG. 16, in the larger-curvature curvedsection 40 h of the light guide 40, even if light leaks from the lightguide 40 as indicated by a dotted arrow A, the light is reflected by thewhite inner surface 23 a of the outer wall 23 and travels in a directionindicated by a dotted arrow B. The light traveling in the directionindicated by the dotted arrow B returns into the light guide 40 orenters the lighting region 21 of the lighting panel 20. Thus, thisconfiguration makes it possible to prevent the lighting region 21 frombecoming dark.

Also, referring to FIG. 17, even if light leaks from the light guide 40in a direction indicated by a dotted arrow C, the light is reflected bythe inner surface 23 a of the outer wall 23 in a direction indicated bya dotted arrow D and returns into the light guide 40 or enters thelighting region 21 of the lighting panel 20. Thus, this configurationmakes it possible to prevent the lighting region 21 from becoming dark.Further, even if light leaks from the light guide 40 in a directionindicated by a dotted arrow E, the light is reflected by the outersurface 24 a of the inner wall 24 in a direction indicated by a dottedarrow F and returns into the light guide 40 or enters the lightingregion 21 of the lighting panel 20. Thus, this configuration makes itpossible to prevent the lighting region 21 from becoming dark.

Here, in the larger-curvature curved sections 40 g and 40 h of the lightguide 40, light may leak out of the light guide 40 and the amount oflight propagating through the light guide 40 may decrease. To compensatefor the light leaked out of the light guide 40, for example, the numberof light-emitting elements may be increased. However, increasing thenumber of light-emitting elements increases the costs of the lightingdevice. The configuration of the lighting device of the presentembodiment makes it possible to prevent the luminance in the lightingregion 21 of the lighting panel 20 from becoming uneven withoutincreasing the costs of the lighting device.

An aspect of this disclosure makes it possible to provide a lightingdevice including a lighting region that has a complex shape but canstill emit light with uniform luminance.

A lighting device according to an embodiment of the present invention isdescribed above. However, the present invention is not limited to thespecifically disclosed embodiment, and variations and modifications maybe made without departing from the scope of the present invention.

What is claimed is:
 1. A lighting device, comprising: a light guide thatpropagates incoming light; and a lighting panel including a lightingregion, wherein a front side of the lighting panel excluding thelighting region is configured to prevent transmission of light; thelight guide is covered by the lighting panel; the lighting device isconfigured such that the light emitted from the light guide passesthrough the lighting region of the lighting panel for illumination; andsurfaces of the lighting panel surrounding the light guide are white incolor, wherein the lighting panel includes an annular outer wallprotruding backward from the front side of the lighting panel where thelighting region is formed, and an annular inner wall provided inside ofthe outer wall and protruding backward from the front side of thelighting panel; the lighting region is formed between the outer wall andthe inner wall; the light guide is disposed in a groove between theouter wall and the inner wall; the outer wall and the inner wall areformed of a material that is same as a material of the surfaces of thelighting panel surrounding the light guide; and the outer wall, theinner wall, and the surfaces of the lighting panel surrounding the lightguide are formed as a monolithic structure.
 2. The lighting device asclaimed in claim 1, wherein each of the light guide and the lightingregion has an annular shape and includes sections having differentcurvatures.
 3. The lighting device as claimed in claim 1, furthercomprising: an operation knob disposed on the front side of the lightingpanel in a region surrounded by the lighting region.